In the related art, for a chair to be used in a room, a seat in a vehicle and the like, a cushion material or a soft pad of which a surface is covered by a cover material is frequently for a part to be touched by a human body such as a seat surface and a back rest. For fixing the cover material, a variety of structures have been adopted. As a structure capable of fixing the cover material and concealing the structure from an outside, a structure where a wire is disposed in a groove of the cushion material, clips are arranged at an edge of the cover material and the clips are engaged to the wire to fasten the cover material has been known.
For example, a cover material fastening clip disclosed in Patent Document 1 or 2 has a chuck part to be locked to a locking end portion attached to a cover material and a hook part to be hooked and locked to a wire provided in a groove of a cushion material. The hook part has a guide piece and a hook arranged side by side to face each other. When a wire is inserted between the guide piece and the hook, the guide piece is bent outwards to widen a gap between the guide piece and the hook, and when the wire is further inserted, the hook is hooked and locked to the wire inserted in the gap.
An example of the cover material fastening clip having the guide piece is shown in FIG. 10. A cover material fastening clip 1 shown in FIG. 10 has a locking part 2 consisting of a pair of locking claws to be locked to a locking end portion attached to a cover material, a hook 3 to be hooked and locked to a wire 6 provided in a groove of a cushion material, and a guide piece 4 arranged side by side to face the hook 3. The hook 3 has an extension portion 3a extending downwards in FIG. 10, a claw-shaped portion 3c bent leftwards from a leading end of the extension portion 3a in FIG. 10 and inclined slightly upwards, and a flange portion 3b extending in an opposite direction (a right direction in FIG. 10) to the extension direction of the claw-shaped portion 3c. The flange portion 3b is inclined so that a leading end thereof faces downwards, and the leading end of the flange portion 3b is provided with a jig support part 5 configured to lock a jig for removing the hook 3 from the wire 6. The guide piece 4 bends and extends downwards, extends through a lateral side of the claw-shaped portion 3c of the hook 3 and reaches a lateral side of the substantially same position as a lower end portion of the flange portion 3b. The cover material fastening clip 1 is configured so that when the wire 6 is inserted between the guide piece 4 and the hook 3, the guide piece 4 is bent outward to widen a gap between the guide piece and the hook 3 and when the wire is further inserted, the hook 3 is hooked and locked to the wire 6 inserted in the gap.
In addition, Patent Document 3 discloses a configuration of hooking and locking the hook to the wire. In the configuration, an opening provided at an upper part of the hook is provided with an elastically deformable cantilever-type closing piece.